The purpose of the Analytical Core is to provide state-of-the art biochemical analysis of sympathetic function, including measurements of catecholamines, their metabolites, and norepinephrine spill over. A variety of techniques have been established in this Core to support individual projects. Biochemical evaluation of sympathetic activity is pivotal. All projects will utilize this resource and will complement other methods of autonomic evaluation detailed in the Clinical Core. Vanderbilt is perhaps the only institution with the expertise to combine functional measurements of sympathetic nerve traffic in humans and advanced biochemical analysis of norepinephrine metabolites and norepinephrine spill over.